G Model AANAT-50709; No. of Pages 6 ARTICLE IN PRESS Annals of Anatomy xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Annals of Anatomy j ournal homepage: www.elsevier.de/aanat Research article Revisiting the anatomy and biomechanics of the anconeus muscle and its role in elbow stability ∗ Barry P. Pereira Musculoskeletal Research Laboratories, Department of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore a r t i c l e i n f o a b s t r a c t Article history: Background: Recent studies have designated the anconeus muscle as an option for use as a pedicled flap Received 9 April 2012 for covering soft tissue defects about the elbow, with reported minimal risk of morbidity. This has raised Received in revised form 9 May 2012 the question as to the importance of the anconeus muscle and as to whether this is truly an accessory Accepted 25 May 2012 muscle that can be sacrificed, or whether the anconeus muscle significantly contributes to elbow and forearm stability? This study revisits the anatomy and biomechanics of the anconeus muscle and aims to Keywords: investigate the neuromuscular compartments of the anconeus muscle and to determine the changes in the Elbow muscle length, fibre length and moment arm over a range of elbow flexion angles for each compartment. Posterolateral stability Methods: An anatomical study on 8 human cadavers (51–77 years of age) was done and a 2-dimensional Neuromuscular compartments kinematic elbow model developed to determine changes in the muscle length and moment arm of the muscle related to changes in elbow flexion angles. Findings: The muscle was modelled with two possible lines of action, one along the posterior and another on the anterior edge of the muscle as they had different muscle fibre lengths (posterior: average of 32 mm, anterior: average of 20 mm). The anterior edge also had an aponeurosis which was 70% of its length. From ◦ 0 to 120 elbow flexion, the length of the posterior and anterior edges increased with a maximum change ◦ recorded at 90 elbow flexion (31.7 ± 1.0 mm and 65.3 ± 1.4 mm, respectively). The moment arm is 14-mm ◦ at 0 flexion, but between the posterior and anterior edges it decreases at different rates with increasing ◦ elbow flexion angle. Beyond 80 , the anterior edge behaves as an elbow flexor, while the posterior edge remains an elbow extensor. The study demonstrates that the anconeus muscle has two neuromuscular compartments each with distinct intramuscular innervations and muscle fibre lengths. Interpretation: The posterior and deep aspect of the muscle functions as an elbow extensor decreasing in influence with increasing elbow flexion angle. The anterior superficial aspect which is adjacent and parallel to the lateral collateral ligaments, would most likely work in unison to provide constraint to the posterolateral stability of the elbow. © 2012 Published by Elsevier GmbH. 1. Introduction (Basmajian and De Luca, 1985; Gleason et al., 1985; Morrey and An, 1985; Morrey et al., 1991). The anconeus muscle is usually described as a triangular- Yet interestingly, recent studies have described the anconeus shaped skeletal muscle with its origin just posterior to the lateral muscle as an option for a pedicled flap for covering soft tissue epicondyle of the humerus, and the muscle fibres fanning out defects about the elbow, with reported minimal risk of morbidity to a broad insertion spanning the posterolateral surface of ulna (Hwang et al., 2004; Nishida et al., 2009; Schmidt et al., 1999). This (Gray et al., 2005; Morrey, 1985; Rosse et al., 1997). Functionally, indeed raises the question as to the importance of the anconeus the anconeus muscle is reported as a weak accessory extensor muscle. Is it an accessory muscle that can be sacrificed or does to the triceps brachii. Some have added that it contributes to the anconeus muscle significantly contribute to elbow and forearm the posterolateral stability of the elbow during forearm rotation stability? Although the stability of the elbow and forearm has been well documented, only a few studies have investigated the posterolateral stability at the elbow. Most data show that the ∗ Correspondence address: Musculoskeletal Research Laboratories, Department lateral collateral ligament complex, comprising of the posterior of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of capsular ligament, the lateral collateral ligaments and the annular Singapore, 10 Kent Ridge Crescent, S119260 Singapore, Singapore. ligaments; constrain the elbow, albeit passively (Cohen and Tel.: +65 6516 5182; fax: +65 6778 0720. E-mail addresses: [email protected], [email protected] Hastings, 1997; Morrey et al., 1991; O’Driscoll et al., 1991; Olsen 0940-9602/$ – see front matter © 2012 Published by Elsevier GmbH. http://dx.doi.org/10.1016/j.aanat.2012.05.007 Please cite this article in press as: Pereira, B.P., Revisiting the anatomy and biomechanics of the anconeus muscle and its role in elbow stability. Ann. Anatomy (2012), http://dx.doi.org/10.1016/j.aanat.2012.05.007 G Model AANAT-50709; No. of Pages 6 ARTICLE IN PRESS 2 B.P. Pereira / Annals of Anatomy xxx (2012) xxx–xxx et al., 1998; Takigawa et al., 2005). In the absence or disruption of done. In all specimens, the skin and soft tissue were first removed this complex, the subluxation of the humeroulnar joint has been exposing the skeletal muscles around the elbow. The various steps demonstrated simulating posterolateral instability of the elbow of the dissection were photo-documented (Fig. 1). Measurements as seen clinically in some reported cases (Hannouche and Begue, of the length of the forearm, and the size and orientation of the ◦ 1999; Imatani et al., 1999). Both studies (Hannouche and Begue, anconeus muscle in situ were taken, with the elbow at 90 flex- 1999; Imatani et al., 1999) further question whether the anconeus ion and forearm in neutral. The lateral epicondyle was used as the muscle would likewise contribute to stabilisation of the elbow reference point. The length of the forearm was taken as the length to varying degrees dependent on elbow flexion positions. Given measured from the olecranon to the distal ulnar styloid. that the anconeus muscle has a close anatomical relationship to In two upper limb specimens, the anconeus muscle was the lateral collateral ligamentous complex (Molinier et al., 2011) removed with its peripheral nerve branch to examine the intra- this investigation revisits the anatomy of the anconeus muscle in muscular innervation and their relationship to the muscle fibres human cadavers and the contributory role of the anconeus muscle and the tendon-like tissue, using the Sihler’s in-toto staining as as a possible active lateral stabiliser of the elbow. The study aimed described previously (Lim et al., 2004; Liu et al., 1997). The pur- at determining the anatomy and morphology of the neuromuscular pose was to investigate the neuromuscular compartments within compartments of the anconeus muscle and hypothesized that the the muscle (English et al., 1993; Weeks and English, 1985). two neuromuscular compartments have changes in their isometric muscle length, fibre length and respective moment arms over a 2.2. Biomechanics range of degrees of elbow flexion. Markers were placed on one specimen, to identify the origin (U) 2. Methods and insertion footprints of the muscle (A, P) on the ulna and for the purpose of developing a 2-D kinematic model to investigate the 2.1. Anatomy changes in the length of the muscle (Fig. 2). This model was based on the line of action being either along the posterior or anterior Eight freshly-frozen human cadaveric upper limbs with no edge of the muscle. Markers were also placed at various bony land- known history of injury or pathology were disarticulated at the markers to establish a local 2-D coordinate system for humerus and glenohumeral joint. Of these, six were right and 2 were left ulna. The humerus was fixed to a frame, and the forearm was pas- ◦ upper limbs. These cadavers, donated for anatomical education and sively flexed from 0 to 120 range of elbow flexion with the forearm research to the Department of Orthopaedic Surgery, National Uni- in neutral rotation. The origin of the humeral coordinate system versity of Singapore were from 6 males of Asian descent and a mean was the lateral epicondyle (O), with the longitudinal axis of the age of 65 years-old (range, 51–77). The specimens were thawed for humerus taken as the humeral y-axis. The origin of the ulnar coor- 24-h at room temperature before the dissection of the tissues was dinate system was at the posterior-end of the footprint insertion of Fig. 1. (A) Dissection of the lateral side of the elbow after removing the skin and surrounding fascia and soft tissue and exposing the anconeus muscle in situ. (B) Isometric measurements of the muscle (note: UP – posterior edge, UA – anterior edge, UT – length of the aponeurosis, PA – isometric length of insertion to the posterolateral aspect ◦ of the ulna, and the distance between the muscle origin, U, with respect to the lateral epicondyle, O) were recorded with the elbow flexed at 90 ). (C) The muscle was subsequently lifted exposing the region deep to the anconeus muscle and (D) released at its origin. Please cite this article in press as: Pereira, B.P., Revisiting the anatomy and biomechanics of the anconeus muscle and its role in elbow stability. Ann. Anatomy (2012), http://dx.doi.org/10.1016/j.aanat.2012.05.007 Download English Version: https://daneshyari.com/en/article/8461342 Download Persian Version: https://daneshyari.com/article/8461342 Daneshyari.com.